The present invention is directed to recirculation control systems or valves, and more particularly to a method and apparatus for monitoring the performance of such systems or valves.
Recirculation control systems are frequently used in centrifugal pump applications to prevent overheating of the pump. Overheating is prevented by maintaining a minimum flow through the pump at all times. During periods of low demand downstream of the pump, the recirculation control system will automatically recirculate enough fluid from the output of the pump to maintain at least the minimum flow through the pump. The recirculated fluid is then directed back to a reservoir.
A recirculation control system may comprise a combination of several valves or a single recirculation control valve. One such valve, disclosed in U.S. Pat. No. 4,967,783 to Loos which is hereby incorporated by reference, is totally self-contained and includes a flow sensing element, a bypass control valve, and a multistage pressure letdown valve all within one body. Other recirculation control valves are disclosed in U.S. Pat. Nos. 4,779,639 and 4,941,502 which are also hereby incorporated by reference.
One disadvantage of a recirculation control system or valve is that it is difficult for plant operating personnel to confirm that it is performing correctly. Unnecessary disassembly and inspection is often performed to inspect specific components. Even disassembly, however, can not confirm that a valve is actually operating properly under all system conditions. In addition, valve inspection and repair is normally performed by trained factory representatives. This presents additional cost and scheduling problems.
Proper performance of recirculation systems at all times is critical to protect the pump. Accordingly, an object of this invention is to monitor valve performance while the valve is in operation.
Another object is to permit monitoring of recirculation control valves in remote locations.
A further object of the invention is to provide a valve performance indicator.
Another object of the invention is to permit continuous monitoring of the valve.